Braze materials and earth-boring tools comprising braze materials

ABSTRACT

A method includes disposing a braze material adjacent a first body and a second body; heating the braze material and forming a transient liquid phase; and transforming the transient liquid phase to a solid phase and forming a bond between the first body and the second body. The braze material includes copper, silver, zinc, magnesium, and at least one material selected from the group consisting of nickel, tin, cobalt, iron, phosphorous, indium, lead, antimony, cadmium, and bismuth.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/584,663, filed Dec. 29, 2014, now U.S. Pat. No. 9,731,384, issuedAug. 15, 2017, which is a continuation-in-part of U.S. patentapplication Ser. No. 14/546,806, filed Nov. 18, 2014, now U.S. Pat. No.9,687,940, issued Jun. 27, 2017, and titled “Methods and Compositionsfor Brazing, and Earth-Boring Tools Formed from Such Methods andCompositions,” the disclosure of each of which is incorporated herein byreference in its entirety.

FIELD

Embodiments of the present disclosure relate generally to methods andmaterials for securing bodies to one another, such as securing cuttingelements to earth-boring drill bits.

BACKGROUND

Downhole tools for earth-boring and for other purposes, including rotarydrill bits, are commonly used in boreholes or wells in earth formations.Cutting elements used in earth-boring tools often includepolycrystalline diamond compact (often referred to as “PDC”) cuttingelements, which are cutting elements that include cutting faces of apolycrystalline diamond material. Polycrystalline diamond material ismaterial that includes inter-bonded grains or crystals of diamondmaterial.

Cutting elements may be secured to a body, such as to fixed-cutterearth-boring rotary drill bits (also referred to as “drag bits”). Suchfixed-cutter bits typically include a plurality of cutting elementsfixedly attached to a bit body of the drill bit, conventionally inpockets formed in blades and other exterior portions of the bit body.Other earth boring tools may include rolling-cone earth-boring drillbits, which include a plurality of roller cones attached to bearing pinson legs depending from a bit body. The roller cones may include cuttingelements (sometimes called “inserts”) attached to the roller cones,conventionally in pockets formed in the roller cones.

Brazing is widely used to join cutting elements to such earth-boringtools and components thereof by means of a braze material (e.g., afiller material) that melts upon heating. The braze material coats thesurfaces of materials being joined, cooling and solidifying to form abond. Braze materials typically wet surfaces of the materials beingjoined and allow the materials to be joined without changing thephysical properties of the materials. Braze materials are conventionallyselected to melt at a lower temperature than a melting temperature ortemperatures of the materials being joined. During a brazing process,heating and cooling of the materials may take place in the openatmosphere, in a controlled atmosphere furnace, or in a vacuum furnace.Braze materials are often alloys based on metals such as Ag, Al, Au, Cu,Ni, Ti, Pd, Pt, Cr, Zr, Sn, Mn, Li, Cd, and alloys thereof. Brazing canbe used effectively to join similar or dissimilar materials (e.g.,metals to metals, ceramics to ceramics, and metals to ceramics).

Typically, in a brazing process, a filler metal or alloy is heated to amelting temperature above 800° F. (427° C.) and distributed between twoor more close-fitting parts by direct placement of the filler materialbetween the parts. In some embodiments, the filler metal or alloy may bedrawn into an interface between the parts by capillary action. At themelting temperature of a braze material, molten braze material interactswith the surfaces of the parts, cooling to form a strong, sealed joint.A brazed joint may thus become a sandwich of different layers, and eachlayer may be metallurgically bonded to one or more adjacent layers.

Brazing cutting elements to an earth-boring tool by conventional methodsmay cause damage to cutting elements, due to the temperatures requiredto melt braze material. Furthermore, removal or repositioning of cuttingelements brazed to a tool typically requires high temperatures, whichcan cause further damage to cutting elements or to the tool body.

BRIEF SUMMARY

In some embodiments, a method includes disposing a braze materialadjacent a first body and a second body; heating the braze material andforming a transient liquid phase; and transforming the transient liquidphase to a solid phase and forming a bond between the first body and thesecond body. The braze material includes copper, silver, zinc,magnesium, and at least one material selected from the group consistingof nickel, tin, cobalt, iron, phosphorous, indium, lead, antimony,cadmium, and bismuth.

In certain embodiments, a braze material includes copper, silver, zinc,magnesium, and at least one material selected from the group consistingof nickel, tin, cobalt, iron, phosphorous, indium, lead, antimony,cadmium, and bismuth.

In some embodiments, a method includes disposing a braze materialbetween a first body and a second body. The braze material includes afirst composition and a second composition. The first composition has afirst melting point, and the second composition has a second meltingpoint higher than the first melting point. The method also includesheating the braze material to a third temperature higher than the firstmelting point and lower than the second melting point and forming atransient liquid phase; and maintaining the braze material above thefirst melting point for a period of time, transforming the transientliquid phase to a solid phase, and forming a bond between the first bodyand the second body.

In some embodiments, a braze material for securing solid bodies includesa first composition and a second composition. The first compositionexhibits a first melting point and includes at least one elementselected from the group consisting of indium, tin, zinc, and magnesium.The second composition exhibits a second melting point higher than thefirst melting point. A solid solution of the first composition and thesecond composition exhibits a melting point between the first meltingpoint and the second melting point.

In some embodiments, an earth-boring tool includes a first body, asecond body, and a braze material bonding the second body to the firstbody. The braze material includes silver, copper, at least one elementselected from the group consisting of nickel and titanium, and at leastone element selected from the group consisting of indium, tin, zinc andmagnesium.

In other embodiments, an earth-boring tool includes a first body, asecond body, and a braze material bonding the second body to the firstbody. The braze material includes silver, copper, zinc, magnesium, andat least one element selected from the group consisting of nickel andtitanium.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming what are regarded as embodiments of the presentdisclosure, various features and advantages of embodiments of thedisclosure may be more readily ascertained from the followingdescription of example embodiments of the disclosure when read inconjunction with the accompanying drawings, in which:

FIGS. 1A through 1C are simplified cross-sectional views illustratingbodies to be brazed and braze materials between the bodies, according tothe present disclosure;

FIG. 2 is a simplified cross-sectional view illustrating the bodies ofany of FIGS. 1A through 1C after brazing;

FIG. 3 is a two-element Ag—In phase diagram illustrating phases ofmaterials at equilibrium as a function of temperature and mass fractionof In;

FIG. 4 is a partial cutaway perspective view of a cutting element;

FIG. 5 is a perspective view of a cutting element secured to a body; and

FIG. 6 is a perspective view of an earth-boring drill bit.

DETAILED DESCRIPTION

The illustrations presented herein are not meant to be actual views ofany particular cutting element, earth-boring tool, or component thereof,but are merely idealized representations that are employed to describeexample embodiments. Thus, the drawings are not necessarily to scale andrelative dimensions may have been exaggerated or understated for thesake of clarity. Additionally, elements common between figures mayretain the same or similar numerical designation.

The term “earth-boring tool” as used herein, means and includes any typeof tool used for drilling during the formation or enlargement of awellbore in a subterranean formation. In some embodiments, earth-boringtools include earth-boring drill bits, such as fixed-cutter bits,rolling-cone bits, impregnated bits, core bits, eccentric bits, bicenterbits, and hybrid bits. In some embodiments, earth-boring tools includereamers, mills, and other drilling tools known in the art.

As used herein, the term “polycrystalline material” means and includesany structure comprising a plurality of grains (i.e., crystals) ofmaterial (e.g., superhard material) that are bonded directly together byinter-granular bonds. The crystal structures of the individual grains ofthe material may be randomly oriented in space within thepolycrystalline material.

As used herein, the terms “inter-granular bond” and “interbonded” meanand include any direct atomic bond (e.g., covalent, metallic, etc.)between atoms in adjacent grains of superabrasive material.

As used herein, the term “tungsten carbide” means and includes anymaterial composition that contains chemical compounds of tungsten andcarbon, such as WC, W₂C, and combinations of WC and W₂C. Tungstencarbide includes, for example, cast tungsten carbide, sintered tungstencarbide, and macrocrystalline tungsten carbide.

As used herein, the term “diamond” means and includes any materialcomposition that contains an allotrope of carbon wherein the carbonatoms are arranged in a diamond lattice structure, typicallycharacterized by a tetrahedral bond structure. Diamond includes, forexample, natural and synthetic diamonds and polycrystalline andmonocrystalline diamond.

As used herein, the term “braze material” means and includes anymaterial for attaching two or more adjacent parts to one another by atleast partially melting and resolidifying the braze material.

As used herein, the term “liquidus” means and includes a temperatureabove which a material is completely liquid at thermal equilibrium. Theterm “solidus” means and includes a temperature below which the materialis completely solid at thermal equilibrium. At temperatures between amaterial's solidus and liquidus, the material exists as a mixture ofsolid and liquid when at thermal equilibrium. For pure substances (e.g.,a pure metal), the solidus and liquidus are the same temperature, whichmay be referred to as the “melting point.” When the term “melting point”is used herein for any material in which the liquidus and solidus arenot identical, “melting point” refers to the solidus, or the point atwhich a solid begins to melt during heating. The terms “melting range”and “solidification range” of a material mean and include thetemperatures between and including the material's solidus and liquidus.

Methods of bonding bodies include disposing a braze material between afirst body and a second body, heating the braze material to a brazingtemperature, and maintaining the brazing temperature of the brazematerial for a period of time to solidify the braze material and form abond between the first body and the second body. The braze materialincludes a first composition having a first melting point and a secondcomposition having a second, higher melting point. The brazingtemperature at which the braze material is held may be higher than thefirst melting point and lower than the second melting point, such thatduring brazing, the first composition melts and the second compositiondoes not. During the bonding process, the first and second compositionsmay mix to form an alloy having a melting point above the brazingtemperature. More specifically, the atoms of the liquid phase formedupon melting the first composition may diffuse into the secondcomposition, and/or one or both of the bodies being bonded, until theliquid phase is at least substantially converted to a solid phase. Thus,the braze material may solidify even before any cooling occurs, or atleast before the bodies and compositions cool to a temperature at orbelow the first melting point of the first composition.

FIG. 1A is a simplified cross-sectional view of a portion of a firstbody 10, a braze material 12, and a second body 14 before the first body10 is bonded to the second body 14. The first body 10 may be, forexample, a bit body, a reamer, a roller cone, a substrate of a cuttingelement, etc. The first body 10 may include one or more metals, such asiron-based steel, another alloy, a metal-matrix composite, tungstencarbide, etc. The second body 14 may include a polycrystalline material,such as diamond, cubic boron nitride, tungsten carbide, etc. Forexample, the second body 14 may be a cutting element that includes apolycrystalline material over (e.g., bonded to) a supporting substrate.In some embodiments, the second body 14 may be a cutting elementincluding a polycrystalline diamond table bonded to a cemented tungstencarbide substrate.

The braze material 12 may include a first composition 13 and a secondcomposition 15 selected to form a mixture upon brazing. The compositions13, 15 may include metals and alloys. In some embodiments, the firstcomposition 13 has a relatively lower solidus or melting point than thesecond composition 15. For example, the first composition 13 may beginto melt at a temperature of less than about 700° C., less than about650° C., less than about 600° C., or even less than about 550° C. Insome embodiments, the second composition 15 may have a solidus ormelting point of at least about 600° C., at least about 700° C., or evenat least about 750° C.

In some embodiments, the first composition 13 may be a commercially puremetal such as indium (In), zinc (Zn), tin (Sn), selenium (Se), bismuth(Bi), antimony (Sb), lead (Pb), etc. The second composition 15 may be,for example, an alloy including one or more of nickel (Ni), cobalt (Co),iron (Fe), silver (Ag), copper (Cu), magnesium (Mg), titanium (Ti),manganese (Mn), or other metals. Either the first composition 13 or thesecond composition 15, or both, may include other materials. Forexample, the first composition 13 may include boron (B), which tends todepress the melting point (solidus) of alloys. In some embodiments, thefirst composition 13 may be a mixture of low-melting-point elements,such as Zn alloyed with Bi, Cd, In, Mg, Sn, and/or Pb. A firstcomposition 13 so formulated may exhibit a melting point even lower thanthe melting point of its major elemental ingredients. Additionalalloying may improve processing and/or the physical properties of theresulting braze material.

The braze material 12 may be disposed between the first body 10 and thesecond body 14. The braze material 12 may be in contact with one or eachof the first body 10 and the second body 14. The braze material 12 orthe compositions 13, 15 thereof may be in the form of a mixture ofmaterials, which may be a moldable solid (e.g., a flux or a paste), asolid having a preformed shape, a powder, a thin sheet (e.g., a foil), awire, or any form as known in the art of brazing and not described indetail herein. The braze material 12 may be applied by disposing thecompositions 13, 15 adjacent to and between the first body 10 and thesecond body 14. For example, the braze material 12 may be pressed to fitthe shape of the first body 10 or the second body 14, sprayed onto thefirst body 10 or the second body 14, etc., and the first body 10 andsecond body 14 may be positioned with the braze material 12 between andin contact with both the first body 10 and the second body 14. In someembodiments, the braze material 12 may be applied as a filler for repairof a previously formed joint.

In some embodiments, the compositions of the braze material 12 may berelatively uniformly admixed in a volume between the first body 10 andthe second body 14. For example, the braze material 12 may be a mixtureof particles of the composition 13 and particles of the secondcomposition 15. In other embodiments, and as depicted in FIG. 1B, eachcomposition of the braze material 12 may be arranged in a layer ordiscrete volume. For example, the compositions of the braze material 12may be formed on or over the first body 10 and/or the second body 14 inlayers. In some embodiments, portions of the first composition 13 of thebraze material 12 may be disposed in contact with each of the first body10 and the second body 14, and the second composition 15 may be disposedbetween the portions of the first composition 13. In other embodiments,the arrangement of the first and second compositions 13, 15 may bereversed, as shown in FIG. 1C. In certain embodiments, the firstcomposition 13 may be in contact with the first body, and the secondcomposition 15 may be in contact with the second body (or vice versa).In other embodiments, the first and second compositions 13, 15 may formadditional layers (e.g., four layers, five layers, six layers, etc.). Ifthe first and second compositions 13, 15 form layers, each layer mayhave a thickness, for example, from about 5 μm to about 2 mm, from about100 μm to about 1 mm, or from about 200 μm to about 500 μm.

The first composition 13 of the braze material 12 may be present in anamount low enough that the first composition 13 does not cause incipientmelting of the second composition 15. For example, the first composition13 may comprise less than about 35% by weight of the braze material 12,less than about 30% by weight of the braze material 12, less than about25% by weight of the braze material 12, or even less than about 20% byweight of the braze material 12.

The first and/or second compositions 13, 15 of the braze material 12 maybe in the form of particulate material. For example, the firstcomposition 13 may include particles having a first average particlesize (e.g., from about 1 μm (micron) to about 15 μm) and the secondcomposition 15 may include particles having a second average particlesize (e.g., from about 25 μm to about 100 μm). One or both of the firstand second compositions 13, 15 may have average particle sizes fromabout 1 nm (nanometer) to about 100 μm, such as from about 30 nm toabout 1 μm, from about 100 nm to about 500 nm, from about 1 μm to about50 μm, or from about 5 μm to about 30 μm. The average particle sizes maybe selected to improve material handling, processing, packing fraction,or other properties. Average particle sizes, as well as the distributionor range of particle sizes, can affect the density, heat transferproperties, and other properties of the braze material 12.

The first body 10, braze material 12, and second body 14 may be heatedto a temperature above a solidus or melting point of the firstcomposition 13 of the braze material 12. The first composition 13 maythen begin to melt, forming a transient liquid phase, without meltingthe second composition 15. In some embodiments, the temperature may bemaintained above a liquidus of the first composition 13. The atomicelements of the molten first composition 13 may diffuse into the secondcomposition 15, forming a modified braze 12′, as shown in FIG. 2, whichmay be completely solid. The modified braze 12′ may be a solid solutionor alloy. The modified braze 12′ may have a liquidus between theliquidus of the first composition 13 and the solidus of the secondcomposition 15. The modified braze 12′ may have a higher solidus thanthe temperature at which the modified braze 12′ is held to melt thefirst composition 13. Thus, the modified braze 12′ may undergo a phasechange to form a solid phase bonded to the first body 10 and the secondbody 14 without melting the second composition 15. Therefore, a mixtureof low- and high-melting-point materials (compositions 13 and 15)processed at relatively low temperatures may form a relativelyhigh-melting-point joint (i.e., the modified braze 12′). In someembodiments, the modified braze 12′ may be a homogeneous orsubstantially homogeneous material. In other embodiments, the modifiedbraze 12′ may have a composition gradient (e.g., a volume of relativelyhigher concentration of a certain species and another volume ofrelatively lower concentration of that species). In other embodiments,the modified braze 12′ may contain small particulate materials formedin-situ or ex-situ providing additional strength to the brazed joint.

Low-temperature processing may allow for more precise gap control (i.e.,control of the spacing between the two bodies, 10, 14) and bettercontrol of the temperature profile (i.e., it may be relatively easier toprecisely control a furnace at lower temperatures than at highertemperatures, allowing consistent formation of robust joints).Low-temperature processing may lessen or eliminate the risk of thermaldamage to temperature-sensitive bodies (e.g., PDC cutters).

For example, to melt the first composition 13, the braze material 12 maybe heated to a temperature from about 200° C. to about 500° C., such asfrom about 200° C. to about 300° C., from about 300° C. to about 400°C., from about 400° C. to about 500° C., or from about 350° C. to about450° C. After the phase change, the modified braze 12′ may exhibit amelting temperature (a solidus, or temperature above which the modifiedbraze 12′ begins to melt) of at least about 550° C., such as at leastabout 600° C., or at least about 650° C.

Processing times for the braze material 12 may be related to theprocessing temperatures, and processing times may be relatively longerthan processing times used for conventional braze materials. Withoutbeing bound to any particular theory, diffusion is believed to berelatively slower at lower processing temperatures than at higherprocessing temperatures. For example, if the first composition 13consists essentially of Zn (having a melting point of about 419° C.),complete sintering of the braze material 12 may occur within about 4 to5 hours at a processing temperature of about 449° C. to about 489° C. Ifthe first composition 13 comprises a mixture of Zn and Mg having asolidus of about 369° C., complete sintering of the braze material 12may occur at a processing temperature of about 399° C. to about 439° C.,but may occur over a relatively longer period of time, such from about 8to 10 hours.

The braze material 12 may be heated in controlled steps in an inertatmosphere. For example, the braze material 12 may be heated in a vacuumor in an environment pressurized with an inert gas (e.g., argon,nitrogen, helium, etc.). Pressure of up to about 1 MPa, up to about 5MPa, up to about 10 MPa, or even up to about 30 MPa may be maintainedthroughout the heating process.

FIG. 3 is a two-element Ag—In phase diagram, illustrating phases ofmaterials at equilibrium as a function of temperature and mass fractionof In (with the balance being Ag). Though the braze material 12disclosed herein may have additional elements, a two-element phasediagram is helpful to illustrate the principle of a phase change thatmay occur when heating the braze material 12. For example, a mixture ofabout 33% In by mass and about 67% Ag by mass is indicated by a dashedvertical line 20. In FIG. 3, points in the area above a liquidus 22 areliquids, and points in the area below the liquidus 22 are phasesincluding one or more solids. If the In and Ag are mixed together asdiscrete solids (e.g., solid particles), the In exhibits a melting pointof about 157° C. and the Ag exhibits a melting point of about 962° C.Thus, heating a mixture of 33% In and 67% Ag will cause the In to meltbefore the Ag melts (i.e., at about 157° C.). The melted In may diffuseinto and around the particles of solid Ag, and may form one or morephases having higher melting points. At equilibrium, as long as thetemperature of the mixture is below the intersection of the verticalline 20 with the liquidus 22, the In at least partially solidifies withAg as solid phase(s). The solid phase(s) have higher liquidus andsolidus than the melting point of pure In and lower liquidus and solidusthan the melting point of pure Ag. Therefore, the process of forming thesolid phase(s) may be carried out at a temperature lower than themelting point of Ag, and even at a temperature lower than the solidus ofthe mixture ultimately formed.

During the phase change, the modified braze 12′ may form solidssubstantially free of intermetallic compounds. As used herein, the term“intermetallic compound” means and includes a solid phase having morethan one metal element in a fixed stoichiometry, with the atoms of eachmetal arranged in an ordered crystalline structure. Intermetalliccompounds may include compounds of relatively high-melting-pointelements (e.g., Co, Ni, Fe, etc.) with relatively low-melting-pointelements (e.g., In, Sn, etc.). For example, intermetallic compounds mayinclude Ni₃Sn, Ni₃In, FeSn, FeSn₂, CoSn, CoSn₂, or Co₃Sn₂, etc. Avoidingintermetallic compounds in the modified braze 12′ may reduce oreliminate embrittlement of the modified braze 12′ or the formation of adiffusion barrier.

In other embodiments, the braze material may be processed in such amanner to form intermetallic compounds. For example, the presence ofparticles of intermetallic compounds having controlled particle sizesand distributions may enhance the strength of a braze material. In suchembodiments, it may be beneficial to form particles of intermetalliccompounds (e.g., as part of the second composition 15) before heatingthe braze material 12. Particles of intermetallic compounds may remainstable during heating of the braze material 12. The type, amount, orparticle size of intermetallic compounds may be controlled to balancevarious properties, such as strength, brittleness, or the formation orproperties of a diffusion barrier.

In some embodiments, other materials may be added to the braze material12, either as part of the first composition 13, the second composition15, or both. For example, nanoparticles such as carbides, oxides,borides, etc. (e.g., tungsten carbide, aluminum oxide), may be added tostrengthen the braze material 12 without interfering with the bonding ofthe braze material 12 to the first body 10 and the second body 14.

Because the braze materials disclosed herein may be applied at a lowertemperature than conventional braze materials, it may be relativelyeasier to braze bodies together with the disclosed braze materials thanwith conventional braze materials. Furthermore, because workingtemperatures may be lower than for conventional braze materials, thermaldamage to tools during brazing may be less likely.

The trend toward homogenization of the braze material 12 during joining(i.e., the brazing process) relies on the kinetics of solid-liquidand/or solid-state diffusion. The kinetics may vary based on factorssuch as temperature, time, particle sizes, shapes of interfaces (e.g.,planar or spherical), cleanliness and uniformity of the braze materialand the bodies to be bonded, atmosphere (e.g., oxygen level), andpressure. Diffusion is typically faster for powder mixtures havingcurved inter-particle interfaces than for mixtures having comparablysized planar interfaces between particles. Diffusion is typically fasterfor powder mixtures having smaller particle sizes than for powdermixtures having larger particle sizes.

In some embodiments, braze material is heated to a temperature higherthan the initial brazing temperature (i.e., the temperature at which thebraze material 12 is held to cause a phase change), and held at thehigher temperature to make the braze material 12 more homogeneous.

Brazing methods and compositions described herein may have propertiessuitable to meet reheating and strength requirements of downhole toolsand drill bits. In some embodiments, an earth-boring tool includes afirst body, a second body, and a braze material bonding the second bodyto the first body. The braze material may include a solid mixture of afirst composition and a second composition, as described above. Thesolid mixture may exhibit a melting point (solidus) between a meltingpoint of the first composition and a melting point of the secondcomposition.

In some embodiments, and as shown in FIG. 4, a cutting element 30includes a polycrystalline material 32 bonded to a substrate 34 by abraze material 36. In some embodiments, the braze material 36 may be themodified braze 12′ described above and shown in FIG. 2. Thus, thepolycrystalline material 32 may correspond to the first body 10 shown inFIG. 2, and the substrate 34 may correspond to the second body 14 shownin FIG. 2. The polycrystalline material 32 may include, for example, adiamond table, cubic boron nitride, or any other hard polycrystallinematerial. The substrate 34 may include, for example, cobalt-cementedtungsten carbide. The braze material 36 may have a melting temperature(a solidus, or temperature above which the braze material 36 begins tomelt) of at least about 550° C., such as at least about 600° C., or atleast about 650° C., after the brazing process.

As shown in FIG. 5, a cutting element 30 may be secured to a body 38 ofan earth-boring tool by braze material 37. The braze material 37 may bethe modified braze 12′ described above and shown in FIG. 2, and may bethe same or different from the braze material 36 shown in FIG. 4.

In some embodiments, and as shown in FIG. 6, an earth-boring bit 40includes a bit body 42 and a plurality of cutting elements 44 secured tothe bit body 42. The cutting elements 44 may include a polycrystallinematerial 46 secured to a substrate 48, such as the cutting elements 30shown in FIG. 4 and described above. In some embodiments, the cuttingelements 44 may include any cutting elements known in the art. Thecutting elements 44 may be secured to the bit body 42 by a brazematerial, such as the modified braze 12′ described above and shown inFIG. 2. Thus, in the earth-boring bit 40 of FIG. 6, the bit body 42 maycorrespond to the first body 10 shown in FIG. 2, and the cuttingelements 44 may correspond to the second body 14 shown in FIG. 2. Thebit body 42 may include, for example, steel, a metal-matrix composite(e.g., cobalt-cemented tungsten carbide), or any other material known inthe art. The braze material may have a melting temperature (a solidus,or temperature above which the braze material begins to melt) of atleast about 550° C., such as at least about 600° C., or at least about650° C., after the brazing process.

In some embodiments, braze material (e.g., the modified braze 12′ shownin FIG. 2, the braze material 36 shown in FIG. 4, or the braze material37 shown in FIG. 5) may be heated to weaken a bond. For example, heatingthe modified braze 12′ may cause the modified braze 12′ to soften,enabling separation of the first body 10 from the second body 14. Such aprocess may be used to separate a polycrystalline material 32 from asubstrate (see FIG. 4), to separate a cutting element 30 from a body 38(see FIG. 5), or to separate a cutting element 44 from a bit body 42(see FIG. 6). Such separations may be beneficial for repair or retoolingof earth-boring bits. For example, cutting elements 44 (FIG. 6) thathave been damaged or that have experienced a predetermined amount ofwear may be removed and replaced before an earth-boring bit 40 isreturned to service. Because the braze material as disclosed herein maybegin to soften and/or melt at a lower temperature than conventionalbraze materials, such separations may be relatively easier to performthan conventionally brazed tools. Furthermore, because workingtemperatures may be lower than for the conventional braze materials,thermal damage to tools during repair and retooling may be less likelyto occur.

In some embodiments, braze material may be heated to a temperature of atleast about 500° C., such as at least about 550° C., or at least about600° C., to soften the braze material sufficient to separate bodies. Thetemperature may be maintained below temperatures at which thermal damageto the brazed bodies occurs (e.g., about 700° C., about 650° C., or evenabout 600° C. for some types of cutting elements). Though the brazematerial may not flow to the extent conventional braze materials flowwhen reheated, the braze material may nonetheless soften enough to allowmanipulation and separation of brazed bodies. Upon separation of brazedbodies, a remnant of the braze material may remain on one or bothbodies. The remnant may be removed by reheating and/or resurfacing thebody. In some embodiments, a remnant of braze material may be left onthe body, and another body may be brazed over the remnant by applyingadditional braze material, during which the remnant of braze materialmay bond with or mix with the additional braze material.

Methods and materials described herein may be used with variouscompositions formulated to exhibit desired strength or other properties.By selectively alloying relatively lower-melting-point materials duringbrazing, brazing may be performed at relatively lower temperatureswithout sacrificing bond strength.

In some embodiments, a barrier material may be disposed over a surfaceof one or more of the bodies to be joined to limit or prevent reactionsof the compositions of the braze material with the material of thebodies. For example, a barrier material may comprise a carbide coating,as described in U.S. Pat. No. 7,487,849, issued Feb. 10, 2009, titled“Thermally Stable Diamond Brazing,” the entire disclosure of which ishereby incorporated by this reference.

The brazing processes may be performed in a furnace or any other meansknown in the art for heating. In some embodiments, the braze materialmay be heated locally, such as by a torch, an electric discharge, etc.In general, furnace heating may provide relatively easier temperaturecontrol, and may be relatively more efficient.

One of the potential risks of using low-melting-point metals in a brazematerial in contact with a steel body (e.g., a steel bit body) orcemented tungsten carbide may be referred to in the art as “liquid metalattack.” In liquid metal attack, selective leaching ofhigh-melting-point elements by low-melting-point liquid may lead tograin boundary damage to the body. The degree of damage is typically afunction of time, temperature, and solubility of the high-melting-pointelement in the liquid. One method of limiting the effect of liquid metalattack is to select braze materials having low solubility in material ofthe bodies to be brazed. For example, indium has relatively lowsolubility in cobalt and iron, so indium may be selected as alow-melting-point composition of a braze for bonding a cobalt-containingbody (e.g., cobalt-cemented tungsten carbide) to an iron-containing body(e.g., steel).

The braze materials disclosed herein may have a relatively narrowsolidification range, defined as the range between the liquidus and thesolidus. Wide solidification ranges, as may be common in conventionalbraze materials, tend to form relatively weaker joints, and tend to berelatively more susceptible to temperature extremes during manufacturingor use. Narrower solidification ranges of the disclosed braze materialsmay correspond to relatively stronger joints and greater resistance totemperature extremes, other factors being equal. In some embodimentsdisclosed herein, the braze materials have solidification ranges ofabout 150° C. or less, about 100° C. or less, or even about 50° C. orless.

Alloy systems with In or Sn as melting point depressants tend to haverelatively large solidification ranges, and the solidus tends to bequite low (e.g., below 500° C.). Large solidification ranges and lowersolidus make such materials undesirable for braze alloys for PDCbonding. However, when combined with Zn, both In and Sn reduce themelting point of Zn further. Therefore, either Zn—In or Zn—Sn alloyedwith Ag—Cu—Ni may form an alloy system useful for earth-boring tools.

EXAMPLES Example 1

A braze composition is prepared from two compositions: an alloyprecursor and a low-melting-point constituent. The alloy precursor,corresponding to the second composition 15 in FIGS. 1A through 1C, is a5-element alloy as shown in Table 1. The low-melting-point constituent,corresponding to the first composition 13 in FIGS. 1A through 1C, iscommercially pure Zn. The compositions are mixed in a ratio of about 73%alloy precursor to 27% low-melting-point constituent. The compositionsmay be mixed together with a binder (e.g., an organic materialformulated to leave no residue deleterious to a joint) to form a paste.The binder is not included in percentages shown in Table 1 because thebinder is expected to be removed from the braze composition duringbrazing.

TABLE 1 Composition (wt. %) Alloy Ag Cu Zn Ni Mg Particle Size AlloyPrecursor 82.2 6.8  5.5 2.7 2.7 1 to 15 μm Low-melting-point — — 100.0 —— −325 mesh Constituent Braze Composition 60.0 5.0  31.0 2.0 2.0

For the braze composition in Table 1, the predicted liquidus isapproximately 630° C. The predicted solidus is approximately 590° C.

Example 2

A braze composition is prepared from two compositions: an alloyprecursor and a low-melting-point constituent. The alloy precursor,corresponding to the second composition 15 in FIGS. 1A through 1C, is a5-element alloy as shown in Table 2. The low-melting-point constituent,corresponding to the first composition 13 in FIGS. 1A through 1C, iscommercially pure Zn. The compositions are mixed in a ratio of about 75%alloy precursor to 25% low-melting-point constituent. The compositionsmay be mixed together with a binder (e.g., an organic materialformulated to leave no residue deleterious to a joint) to form a paste.The binder is not included in percentages shown in Table 2 because thebinder is expected to be removed from the braze composition duringbrazing.

TABLE 2 Composition (wt. %) Alloy Ag Cu Zn Ti Mg Particle Size AlloyPrecursor 78.0 11.3  5.3 2.7 2.7 1 to 15 μm Low-melting-point — — 100.0— — −325 mesh Constituent Braze Composition 58.5  8.5  29.0 2.0 2.0

For the braze composition in Table 2, the predicted liquidus isapproximately 630° C. The predicted solidus is approximately 538° C.

Example 3

A braze composition is prepared from two compositions: an alloyprecursor and a low-melting-point constituent. The alloy precursor,corresponding to the second composition 15 in FIGS. 1A through 1C, is a4-element alloy as shown in Table 3. The low-melting-point constituent,corresponding to the first composition 13 in FIGS. 1A through 1C, iscommercially pure Zn. The compositions are mixed in a ratio of about 72%alloy precursor to 28% low-melting-point constituent. The compositionsmay be mixed together with a binder (e.g., an organic materialformulated to leave no residue deleterious to a joint) to form a paste.The binder is not included in percentages shown in Table 3 because thebinder is expected to be removed from the braze composition duringbrazing.

TABLE 3 Composition (wt. %) Alloy Ag Cu Zn In Ni Particle Size AlloyPrecursor 70.8 25.0 2.8 1.4 1 to 15 μm Low-melting-point — — 100.0 — —−325 mesh Constituent Braze Composition 51.0 18.0  28.0 2.0 1.0

For the braze composition in Table 3, the predicted liquidus isapproximately 675° C. The predicted solidus is approximately 642° C.

Example 4

A braze composition is prepared from two compositions: an alloyprecursor and a low-melting-point constituent. The alloy precursor,corresponding to the second composition 15 in FIGS. 1A through 1C, is a4-element alloy as shown in Table 4. The low-melting-point constituent,corresponding to the first composition 13 in FIGS. 1A through 1C, iscommercially pure Zn. The compositions are mixed in a ratio of about 72%alloy precursor to 28% low-melting-point constituent. The compositionsmay be mixed together with a binder (e.g., an organic materialformulated to leave no residue deleterious to a joint) to form a paste.The binder is not included in percentages shown in Table 4 because thebinder is expected to be removed from the braze composition duringbrazing.

TABLE 4 Composition (wt. %) Alloy Ag Cu Zn In Ni Particle Size AlloyPrecursor 72.2 20.8 5.6 1.4 1 to 15 μm Low-melting-point — — 100.0 — —−325 mesh Constituent Braze Composition 52.0 15.0  28.0 4.0 1.0

For the braze composition in Table 4, the predicted liquidus isapproximately 686° C. The predicted solidus is approximately 631° C.

Example 5

A braze composition is prepared from two compositions: an alloyprecursor and a low-melting-point constituent. The alloy precursor,corresponding to the second composition 15 in FIGS. 1A through 1C, is a5-element alloy as shown in Table 5. The low-melting-point constituent,corresponding to the first composition 13 in FIGS. 1A through 1C, iscommercially pure Zn. The compositions are mixed in a ratio of about 75%alloy precursor to 25% low-melting-point constituent. The compositionsmay be mixed together with a binder (e.g., an organic materialformulated to leave no residue deleterious to a joint) to form a paste.The binder is not included in percentages shown in Table 5 because thebinder is expected to be removed from the braze composition duringbrazing.

TABLE 5 Composition (wt. %) Alloy Ag Cu Zn Ti Mg Particle Size AlloyPrecursor 78.7 12.0  5.3 2.0 2.0 1 to 15 μm Low-melting-point — — 100.0— — −325 mesh Constituent Braze Composition 59.0  9.0  29.0 1.5 1.5

For the braze composition in Table 5, the predicted liquidus isapproximately 630° C. The predicted solidus is approximately 590° C.

Additional non-limiting example embodiments of the disclosure aredescribed below.

Embodiment 1

A method comprising disposing a braze material between a first body anda second body. The braze material comprises a first composition and asecond composition, the first composition having a first melting pointand the second composition having a second melting point higher than thefirst melting point. The method further comprises heating the brazematerial to a third temperature higher than first melting point andlower than the second melting point and forming a transient liquidphase; and maintaining the braze material above the first melting pointfor a period of time, transforming the transient liquid phase to a solidphase, and forming a bond between the first body and the second body.

Embodiment 2

The method of Embodiment 1, wherein the second composition comprises analloy.

Embodiment 3

The method of Embodiment 2, wherein the second composition comprises analloy comprising at least one element selected from the group consistingof silver, copper, manganese, nickel, titanium, cobalt, and aluminum.

Embodiment 4

The method of any of Embodiments 1 through 3, wherein the firstcomposition comprises at least one element selected from the groupconsisting of indium, tin, zinc, and magnesium.

Embodiment 5

The method of any of Embodiments 1 through 4, wherein solidifying thetransient liquid phase comprises forming a solid substantially free ofintermetallic compounds.

Embodiment 6

The method of any of Embodiments 1 through 5, wherein disposing a brazematerial between the first body and the second body comprises disposinga paste comprising at least a composition of the braze material betweenthe first body and the second body.

Embodiment 7

The method of any of Embodiments 1 through 6, wherein disposing a brazematerial between the first body and the second body comprises disposinga thin sheet comprising at least a composition of the braze materialbetween the first body and the second body.

Embodiment 8

The method of any of Embodiments 1 through 7, wherein heating the brazematerial to a third temperature higher than first melting point andlower than the second melting point comprises heating the braze materialto a temperature in a range extending from about 200° C. to about 600°C.

Embodiment 9

The method of any of Embodiments 1 through 8, further comprising, afterthe bonded first body and second body are used in an application,heating the solidified braze material to a fourth temperature to weakenthe bond between the first body and the second body.

Embodiment 10

The method of Embodiment 9, wherein heating the solidified brazematerial to a fourth temperature to weaken the bond between the firstbody and the second body comprises heating the solidified braze materialto a temperature in a range extending from about 600° C. to about 800°C.

Embodiment 11

The method of Embodiment 9 or Embodiment 10, further comprisingseparating the first body from the second body.

Embodiment 12

The method of any of Embodiments 1 through 11, wherein disposing a brazematerial between a first body and a second body comprises disposing thebraze material between polycrystalline diamond and a metal body.

Embodiment 13

The method of any of Embodiments 1 through 12, wherein disposing a brazematerial between a first body and a second body comprises disposing abraze material between a polycrystalline material and a metal matrixcomposite.

Embodiment 14

The method of any of Embodiments 1 through 13, wherein disposing a brazematerial between a first body and a second body comprises disposing afirst volume of the second composition adjacent and in contact with thefirst body, disposing a second volume of the second composition adjacentand in contact with the second body, and disposing a volume of the firstcomposition adjacent and in contact with the first volume and secondvolume of the second composition.

Embodiment 15

A braze material comprising a first composition and a secondcomposition. The first composition exhibits a first melting point andincludes at least one element selected from the group consisting ofindium, tin, zinc, and magnesium. The second composition exhibits asecond melting point higher than the first melting point. A solidsolution of the first composition and the second composition exhibits amelting point between the first melting point and the second meltingpoint.

Embodiment 16

The braze material of Embodiment 15, wherein the first compositioncomprises an element selected from the group consisting of indium andtin.

Embodiment 17

The braze material of Embodiment 15 or Embodiment 16, wherein the secondcomposition comprises at least one element selected from the groupconsisting of silver, copper, manganese, nickel, titanium, cobalt, andaluminum.

Embodiment 18

The braze material of Embodiment 15, wherein the first compositioncomprises indium and the second composition comprises nickel and cobalt.

Embodiment 19

The braze material of Embodiment 15, wherein the first compositioncomprises tin and the second composition comprises nickel and cobalt.

Embodiment 20

The braze material of any of Embodiments 15 through 19, wherein thefirst composition comprises a first plurality of particles, and thesecond composition comprises a second plurality of particlesinterspersed with the first plurality of particles.

Embodiment 21

The braze material of any of Embodiments 15 through 19, wherein thefirst composition comprises a first layer of material and the secondcomposition comprises a second layer of material.

Embodiment 22

The braze material of any of Embodiments 15 through 21, furthercomprising an organic binder material.

Embodiment 23

The braze material of any of Embodiments 15 through 22, wherein thebraze material comprises from about 50% to about 70% silver by weightand from about 4% to about 20% copper by weight.

Embodiment 24

The braze material of any of Embodiments 15 through 22, wherein thebraze material comprises from about 20% to about 35% elements selectedfrom the group consisting of indium, tin, zinc, and magnesium by weight.

Embodiment 25

An earth-boring tool, comprising a first body, a second body, and abraze material bonding the second body to the first body. The brazematerial comprises silver, copper, at least one element selected fromthe group consisting of nickel and titanium, and at least one elementselected from the group consisting of indium, tin, zinc, and magnesium.

Embodiment 26

An earth-boring tool, comprising a first body, a second body, and abraze material bonding the second body to the first body. The brazematerial comprises silver, copper, zinc, magnesium, and at least oneelement selected from the group consisting of nickel and titanium.

Embodiment 27

The earth-boring tool of Embodiment 25 or Embodiment 26, wherein thebraze material comprises a solid substantially free of intermetalliccompounds.

Embodiment 28

The earth-boring tool of any of Embodiments 25 through 27, wherein thefirst body comprises a bit body.

Embodiment 29

The earth-boring tool of Embodiment 28, wherein the bit body comprises ametal matrix material.

Embodiment 30

The earth-boring tool of any of Embodiments 25 through 29, wherein thesecond body comprises a polycrystalline material.

Embodiment 31

The earth-boring tool of Embodiment 30, wherein the polycrystallinematerial comprises polycrystalline diamond.

Embodiment 32

The earth-boring tool of Embodiment 31, wherein the polycrystallinediamond comprises a diamond table, and wherein the first body comprisesa tungsten carbide substrate.

Embodiment 33

The earth-boring tool of Embodiment 30, wherein the polycrystallinematerial comprises cubic boron nitride.

Embodiment 34

A method comprising disposing a braze material adjacent a first body anda second body; heating the braze material and forming a transient liquidphase; and transforming the transient liquid phase to a solid phase andforming a bond between the first body and the second body. The brazematerial comprises copper, silver, zinc, magnesium, and at least onematerial selected from the group consisting of nickel, tin, cobalt,iron, phosphorous, indium, lead, antimony, cadmium, and bismuth.

Embodiment 35

The method of Embodiment 34, wherein disposing a braze material adjacenta first body and a second body comprises disposing a braze materialcomprising at least one intermetallic compound adjacent the first bodyand the second body.

Embodiment 36

The method of Embodiment 34 or Embodiment 35, wherein disposing a brazematerial adjacent a first body and a second body comprises disposing abraze material comprising a plurality of particles adjacent the firstbody and the second body.

Embodiment 37

The method of Embodiment 36, wherein disposing a braze materialcomprising a plurality of particles adjacent the first body and thesecond body comprises disposing a braze material comprising a pluralityof particles having an average particle size in a range from about 1 μmto about 15 μm adjacent the first body and the second body.

Embodiment 38

The method of any of Embodiments 34 through 37, wherein disposing abraze material adjacent the first body and the second body comprisesdisposing a paste comprising at least a composition of the brazematerial adjacent the first body and the second body.

Embodiment 39

The method of any of Embodiments 34 through 38, wherein disposing abraze material adjacent the first body and the second body comprisesdisposing a thin sheet comprising at least a composition of the brazematerial adjacent the first body and the second body.

Embodiment 40

The method of any of Embodiments 34 through 39, wherein heating thebraze material and forming a transient liquid phase comprises heatingthe braze material to a temperature in a range extending from about 200°C. to about 600° C.

Embodiment 41

The method of any of Embodiments 34 through 40, further comprising,after the bonded first body and second body are used in an application,heating the solidified braze material to weaken the bond between thefirst body and the second body.

Embodiment 42

The method of Embodiment 41, wherein heating the solidified brazematerial to weaken the bond between the first body and the second bodycomprises heating the solidified braze material to a temperature in arange extending from about 600° C. to about 800° C.

Embodiment 43

The method of Embodiment 41 or Embodiment 42, further comprisingseparating the first body from the second body.

Embodiment 44

The method of any of Embodiments 34 through 43, wherein disposing abraze material adjacent a first body and a second body comprisesdisposing the braze material adjacent a previously formed joint betweenthe first body and the second body.

Embodiment 45

The method of any of Embodiments 34 through 44, wherein heating thebraze material and forming a transient liquid phase comprises heatingthe braze material for at least about four hours.

Embodiment 46

The method of any of Embodiments 34 through 45, wherein heating thebraze material and forming a transient liquid phase comprises heatingthe braze material in an inert atmosphere.

Embodiment 47

A braze material comprising copper, silver, zinc, magnesium, and atleast one material selected from the group consisting of nickel, tin,cobalt, iron, phosphorous, indium, lead, antimony, cadmium, and bismuth.

Embodiment 48

The braze material of Embodiment 47, wherein the braze materialcomprises metallic particles having an average particle size in a rangefrom about 1 μm to about 15 μm.

Embodiment 49

The braze material of Embodiment 47 or Embodiment 48, further comprisingan organic binder.

Embodiment 50

The braze material of any of Embodiments 47 through 49, wherein thebraze material comprises a first plurality of metallic particles and asecond plurality of metallic particles interspersed with the firstplurality of metallic particles.

Embodiment 51

The braze material of Embodiment 50, wherein the first plurality ofmetallic particles comprises a first material having a first compositionand the second plurality of metallic particles comprises a secondmaterial having a second composition different from the firstcomposition.

Embodiment 52

The braze material of any of Embodiments 47 through 51, wherein thebraze material comprises at least one intermetallic compound.

Embodiment 53

The braze material of any of Embodiments 47 through 52, furthercomprising nanoparticles comprising at least one material selected fromthe group consisting of carbides, oxides, and borides.

While the present invention has been described herein with respect tocertain illustrated embodiments, those of ordinary skill in the art willrecognize and appreciate that it is not so limited. Rather, manyadditions, deletions, and modifications to the illustrated embodimentsmay be made without departing from the scope of the invention ashereinafter claimed, including legal equivalents thereof. In addition,features from one embodiment may be combined with features of anotherembodiment while still being encompassed within the scope of theinvention as contemplated by the inventors. Further, embodiments of thedisclosure have utility with different and various types andconfigurations of tools.

What is claimed is:
 1. A braze material comprising: copper; from about50% to about 70% silver by weight; from about 25% to about 35% zinc byweight; magnesium; and at least one material selected from the groupconsisting of nickel, tin, cobalt, iron, phosphorous, indium, lead,antimony, cadmium, and bismuth.
 2. The braze material of claim 1,wherein the braze material comprises metallic particles having anaverage particle size in a range from about 1 μm to about 15 μm.
 3. Thebraze material of claim 1, further comprising an organic binder.
 4. Thebraze material of claim 1, wherein the braze material comprises a firstplurality of metallic particles and a second plurality of metallicparticles interspersed with the first plurality of metallic particles.5. The braze material of claim 4, wherein the first plurality ofmetallic particles comprises a first material having a first compositionand the second plurality of metallic particles comprises a secondmaterial having a second composition different from the firstcomposition.
 6. The braze material of claim 1, wherein the brazematerial comprises at least one intermetallic compound.
 7. The brazematerial of claim 1, further comprising nanoparticles comprising atleast one material selected from the group consisting of carbides,oxides, and borides.
 8. The braze material of claim 7, wherein thenanoparticles comprise tungsten carbide.
 9. The braze material of claim7, wherein the nanoparticles comprise aluminum oxide.
 10. The brazematerial of claim 6, wherein the braze material comprises at least oneintermetallic compound selected from the group consisting of Ni₃Sn,Ni₃In, FeSn, FeSn₂, CoSn, CoSn₂, and Co₃Sn₂.
 11. The braze material ofclaim 1, wherein the braze material comprises indium.
 12. The brazematerial of claim 1, wherein the braze material comprises tin.
 13. Thebraze material of claim 1, wherein the braze material comprises fromabout 5% to about 9% copper by weight.
 14. The braze material of claim1, wherein the braze material comprises from about 58.5% to about 60%silver by weight.
 15. The braze material of claim 1, wherein the brazematerial comprises from about 1.5% to about 2% magnesium by weight. 16.The braze material of claim 1, wherein the braze material comprisestitanium.
 17. An earth-boring tool, comprising: a first body, a secondbody; and a braze material bonding the second body to the first body,the braze material comprising: copper; from about 50% to about 70%silver by weight; from about 25% to about 35% zinc by weight; magnesium;at least one material selected from the group consisting of nickel, tin,cobalt, iron, phosphorous, indium, lead, antimony, cadmium, and bismuth.